Polk Sarah E, Kleemeyer Maike M, Bodammer Nils C, Misgeld Carola, Porst Johanna, Wolfarth Bernd, Kühn Simone, Lindenberger Ulman, Düzel Sandra, Wenger Elisabeth
Center for Lifespan Psychology, Max Planck Institute for Human Development, Berlin, Germany.
International Max Planck Research School on the Life Course (LIFE), Berlin, Germany.
Neuroimage Rep. 2023 Jan 4;3(1):100155. doi: 10.1016/j.ynirp.2022.100155. eCollection 2023 Mar.
White matter integrity and cognition have been found to decline with advancing adult age. Aerobic exercise may be effective in counteracting these declines. Generally, white matter integrity has been quantified using a volumetric measure (WMV) and with tensor-based parameters, such as fractional anisotropy (FA) and mean diffusivity (MD), the validity of which appears to be compromised in the presence of crossing fibers. Fixel-based analysis techniques claim to overcome this problem by yielding estimates of fiber density (FD), cross-section (FC), and their product (FDC) in multiple directions per voxel. In a sample of 61 healthy older adults (63-76 years old), we quantified changes in white matter integrity following an aerobic exercise intervention with the commonly used volumetric and tensor-based metrics (WMV, FA, MD) and with fixel-based metrics (FD, FC, FDC). We investigated the associations of changes in these white matter parameters with changes in cardiovascular fitness and Digit Symbol Substitution task (DSST) performance, a marker of perceptual speed. In line with previous findings, we observed maintained WMV in the corpus callosum of exercisers, and positive change-change correlations between WMV and fitness, and between WMV and perceptual speed. For FA and MD, group differences in change opposite to those hypothesized were found in the corpus callosum, posterior corona radiata, and superior longitudinal fasciculus at an uncorrected significance threshold. Likewise, regions in superficial WM in the prefrontal cortex showed group differences in FD and FDC change, uncorrected, with more positive change in controls and more negative change in exercisers. Finally, changes in FD and FDC were found to be inversely correlated to changes in fitness and DSST performance. The present results corroborate previous findings of WMV changes, but cast doubt on current physiological interpretations of both tensor-based and fixel-based indicators of white matter properties in the context of exercise intervention studies.
随着成年年龄的增长，白质完整性和认知能力会出现下降。有氧运动可能有效地对抗这些下降。一般来说，白质完整性已通过体积测量法（WMV）以及基于张量的参数（如分数各向异性（FA）和平均扩散率（MD））进行量化，然而在交叉纤维存在的情况下，这些参数的有效性似乎会受到影响。基于体素的分析技术声称通过在每个体素的多个方向上得出纤维密度（FD）、横截面积（FC）及其乘积（FDC）的估计值来克服这一问题。在61名健康老年人（63 - 76岁）的样本中，我们使用常用的体积测量法和基于张量的指标（WMV、FA、MD）以及基于体素的指标（FD、FC、FDC），对白质完整性在有氧运动干预后的变化进行了量化。我们研究了这些白质参数的变化与心血管健康状况变化以及数字符号替换任务（DSST）表现（一种感知速度的指标）之间的关联。与先前的研究结果一致，我们观察到运动者胼胝体中的WMV保持不变，并且WMV与健康状况之间以及WMV与感知速度之间存在正的变化 - 变化相关性。对于FA和MD，在未校正的显著性阈值下，胼胝体、放射冠后部和上纵束中发现的变化的组间差异与假设的相反。同样，前额叶皮质浅层白质区域在未校正的情况下显示出FD和FDC变化的组间差异，对照组的变化更为正向，而运动者的变化更为负向。最后，发现FD和FDC的变化与健康状况和DSST表现的变化呈负相关。目前的结果证实了先前关于WMV变化的研究结果，但对运动干预研究背景下基于张量和基于体素的白质特性指标的当前生理学解释提出了质疑。
